Fig. 4: Depth-dependent XPS profiles for the cleaved Cu electrode side.
From: Tracking the evolution of materials and interfaces in perovskite solar cells under an electric field
a–c The distributions of N, I, Pb, and Cu for PSCs with and without electric stress. a 0 V, b −1 V, and c + 1 V. The difference spectra (raw data minus Cu0 reference spectrum55, noted as the dashed line in the Cu LMM graph) show the Cu electrode are mainly Cu0 feature, indicating the Cu electrode is not affected by the diffused I2 significantly. The differentiation between metal and oxides of copper’s chemical states is indistinguishable in Cu 2p XPS spectra. Thus, the Cu LMM Auger spectra are used to help assign chemistry56. The Cu 2p3/2 spectra of these corresponding samples are provided in Supplementary Fig. 4.
